The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
A present-day ion thruster block-diagram is illustrated in FIG. 1. The ion thruster 10 creates a plasma using a gas (e.g. Xe) fed into a chamber 12 and allows the ions as an ion beam 14 to escape across an accelerating grid structure 16. There are several practical limitations to the ion thruster 10 of FIG. 1: (1) the ionization process represents an important life-limiting factor, (2) an important fraction of the propellant is never ionized, and (3) the plasma interacts with the walls and the grid, thus generating waste heat and limiting the lifetime of ion thruster 10.
The concept of utilizing field emission and electrostatic acceleration of ions is well known as Field Emission Electric Propulsion (FEEP). FEEP thrusters can produce specific impulses above 10,000 seconds at electrical efficiencies exceeding 90% using melted metal liquid propellant such as indium. However, known FEEPs use needle-like emitters that require footprints many times wider than the needle tips. Thus, their potential for being scaled-up to multi-kW power levels is doubtful.